Phase difference element and optical head apparatus
a technology of phase difference element and optical head, which is applied in the direction of polarising element, record information storage, instruments, etc., can solve the problems of cost reduction and miniaturization of the apparatus
Inactive Publication Date: 2010-05-27
ASAHI GLASS CO LTD
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Benefits of technology
The present invention relates to a phase difference element for changing the polarization state of light incident on an optical disk. The technical effect of the invention is to provide a phase difference element that has three or more peaks at which ellipticity approximates to 1 when light of linear polarization enters in a predetermined wavelength range (380 to 900 nm) and also has constant ellipticity even at a wavelength other than the peaks. This allows for better utilization of light and improved reliability of the optical head apparatus.
Problems solved by technology
In this case, for example, an optical head apparatus for recording or reproducing an optical disk with plural standards has a light source with plural wavelengths, so that it is necessary to respectively comprise quarter-wave plates according to light of the plural wavelengths and a disadvantage occurred in cost reduction and miniaturization of the apparatus.
Method used
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Embodiment Construction
[0050]FIG. 1 shows a schematic diagram of a sectional structure of a phase difference element 1 according to the present embodiment. The phase difference element 1 is constructed of three phase difference layers of a first phase difference layer 11, a second phase difference layer 12 and a third phase difference layer 13 made of a material having refractive index anisotropy from the side in which light of linear polarization is entered. These phase difference layers have an integrated configuration by laminating the layers through an adhesive layer or a sticky layer or fusing or welding the layers and thereby, the number of components reduces and laminating accuracy improves and characteristics of the phase difference element are stable. Also, when the layers can be laminated substantially even in the absence of the adhesive layer, further miniaturization can be achieved and this is preferable. Also, these phase difference layers may be laminated on a transparent substrate, or the p...
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Abstract
Three phase difference layers having refractive index anisotropy are stacked in parallel and an optic axis angle and retardation of each of the phase difference layers are adjusted and thereby, characteristics having peaks at which ellipticity is approximated to 1 at desired three design wavelengths can be obtained and it can efficiently be adapted to an optical head apparatus for converting linear polarization of a light source with, for example, three different wavelengths into circular polarization.
Description
TECHNICAL FIELD[0001]The present invention relates to a phase difference element for changing a polarization state of light, and an optical head apparatus for making recording or reproduction with respect to an optical recording medium (hereinafter called an optical disk) such as a CD, a DVD, a Blue-ray disk (hereinafter called a BD) or an HD-DVD.BACKGROUND ART[0002]This kind of optical head apparatus comprises a light source and an optical detector, an optical path separation element such as a beam splitter for reflecting an optical beam emitted from the light source so as to guide the optical beam to an optical disk and also transmitting reflected light from the optical disk so as to guide the reflected light toward the optical detector, and an objective lens arranged oppositely to an information recording surface of the optical disk. Particularly, a quarter-wave plate (λ / 4 plate) for rotating a polarization plane of light incident on and reflected by the optical disk, that is, ch...
Claims
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IPC IPC(8): G11B7/135G02B27/28
CPCG02B5/3083G11B2007/0006G11B7/1369G11B7/1365
Inventor MURATA, KOICHIKAKIUCHI, TOSHIMASA
Owner ASAHI GLASS CO LTD